Bacterial cell membrane (Gram-positive)

The bacterial cell membrane of Gram-positive species is a vital phospholipid bilayer that serves as the primary boundary between the cytoplasm and the external environment (Sohlenkamp & Geiger, 2016). Unlike Gram-negative bacteria, Gram-positive organisms lack an outer membrane but possess a thick, porous peptidoglycan cell wall that allows antimicrobial molecules to reach the underlying cytoplasmic membrane (Silhavy et al., 2010). This membrane is essential for maintaining the electrochemical gradient, facilitating nutrient transport, and anchoring enzymes involved in cell wall synthesis and energy production (Strahl & Hamoen, 2010). It is a major therapeutic target for lipopeptide antibiotics like daptomycin, which selectively bind to the membrane's anionic phospholipids, such as phosphatidylglycerol (Muller et al., 2016). Disruption of this membrane leads to the loss of membrane potential, leakage of intracellular ions, and rapid cessation of macromolecular synthesis, ultimately resulting in bacterial cell death (Silverman et al., 2003). Because bacterial membranes differ significantly from mammalian membranes in lipid composition and lack cholesterol, they offer a high degree of selectivity for antimicrobial agents (Epand et al., 2016). Therapeutic agents targeting this structure are particularly effective against multi-drug resistant Gram-positive pathogens like MRSA and VRE (Ling et al., 2015). However, bacteria can develop resistance by altering their membrane charge or lipid composition to repel cationic antibiotics (Bayer et al., 2013).

Other names

Gram-positive cytoplasmic membraneBacterial plasma membraneGram-positive inner membrane

Drugs targeting the Gram-positive bacterial cell membrane typically act by disrupting membrane integrity, causing depolarization, or forming pores (Muller et al., 2016). For instance, daptomycin inserts into the membrane in a calcium-dependent manner, leading to potassium efflux and rapid cell death without lysis (Silverman et al., 2003). Other agents, such as certain glycopeptides and lipopeptides, may bind to membrane-associated lipid precursors like lipid II to inhibit cell wall synthesis while simultaneously perturbing the membrane's physical structure (Ling et al., 2015).